The quick adoption of electric vehicles (EVs) requires a unified interoperable charging infrastructure across the EU. The H2020 project USER-CHI aims at devising the guidelines for an interoperable charging infrastructure for EVs. To make access to the charging infrastructure possible irrespectively of vehicle brands and operators, an analysis of the existing interoperability framework was considered essential within the USER-CHI project. Pursuant to this, IKEM developed INFRA (INteroperability FRAmework), a study that contains an analysis of the four layers that condition interoperability in the electromobility sector (organizational, semantic, technical, legal). This paper aims at giving publicity to INFRA and to add new inputs on some of the most relevant aspects through literature review.